Allison 1000 temperature rise

[MFritch]

I have a 2002 GMC 2500 HD Crewcab with the Duramax and Allison. I am also running a VanAaken module at 110 hp and I’m at about 190,000 miles. For the first 160,000 miles I never saw the transmission temperature rise above ~120°. Lately it runs at about 155-160° and up to 175-180° when pulling a trailer, in hot weather or high speed driving on I-5 going over the Siskiyous. I’m wondering about the need for rebuilding the transmission soon or if the slight rise in temperatures is normal. What are your thoughts? I’d like to take care of any problems before they become serious.

[DmaxMaverick]

Sounds like it's on the "chilly" side. Are you sure it is 120 to 160 (and not 220 to 260)? As long as you are not in the red, it's fine. If you worry about it, put in synthetic fluid. 160° is operating temp. Heavier loads will cause higher tranny temps, as will higher ambient temps.